Phosphorylation of Kv7 potassium channels by protein kinase C in human airway smooth muscle cells

Abstract

In previous studies, bronchoconstrictor agonists inhibited Kv7 potassium currents in guinea pig airway smooth muscle cells (ASMCs) and the selective Kv7 channel blocker XE991 induced severe bronchoconstriction in human precision cut lung slices (PCLS). However, the mechanism of regulation of airway Kv7 channels is unknown. In the present study, we investigated protein kinase C (PKC)‐induced phosphorylation and inhibition of Kv7 channels. The ability of PKC activator phorbol 12‐myristate 13‐acetate (PMA) to induce bronchoconstriction was examined using human PCLS. We found that PMA induced robust constriction of human airways. Immunoprecipitation and western blot analysis were used to detect phosphorylation of Kv7.5 channels in response to histamine or PMA using human trachealis smooth muscle cells (HTSMCs) infected with a FLAG‐tagged human Kv7.5 adenoviral vector. Both treatments caused increased FLAG‐Kv7.5 phosphorylation. Histamine inhibited Kv7.5 currents in HTSMCs but that effect was abolished when cells were pretreated with the PKC inhibitor calphostin C. Our findings suggest a role of PKC‐induced phosphorylation in the suppression of Kv7 channels in ASMCs. (Funded by Loyola University Chicago.)